1. Field of the Invention
The present invention relates to an electronic blood pressure monitor for determining a blood pressure value using a pulse wave and, more particularly, to an electronic blood pressure monitor for determining a blood pressure value based on a wave feature value of the wave pulse.
2. Description of the Related Art
In a blood pressure measuring method using a conventional electronic blood pressure monitor, a blood pressure measuring method using one pulse wave is suggested. This method calculates a blood pressure according to a probability density function for defining a relationship between a wave feature value such as an average level and a peak width of a pulse waveform actually measured based on a waveform of a pulse wave detected originally based on pressure oscillation generated when a cuff is attached to an upper arm portion and the cuff is pressured, namely, a pulse wave component of a volumetric change of an artery, and a relative cuff pressure based on a blood pressure value. This method does not require a new measuring system and an input signal, and can calculate a blood pressure based on a pulse wave signal of only one pulse. The blood pressure value is calculated at a pressure level of an arbitrary one point in entire interval of a pressure to be applied to the cuff.
However in such a conventional electronic blood pressure monitor, since also a portion at a low level of a pulse wave signal is used for calculating a blood pressure value, a noise component included in the detected pulse wave signal becomes large, and an S/N ratio becomes small. As a result, in the detection of the pulse wave, the calculation of the wave feature value of a pulse wave and calculation of the blood pressure value based on the calculated wave feature value, an error factor becomes large. As a result, it is difficult to obtain a blood pressure value with high accuracy.